The types of machinery on which industrial machinery mechanics work are as varied as the types of industries operating in the United States today, but include automobile assembly line conveyor belts, robotic welding arms, and hydraulic lifts. Mechanics are employed in metal stamping plants, printing plants, chemical and plastics plants, and almost any type of large-scale industrial operation that can be imagined. The machinery in these plants must be maintained regularly. Breakdowns and delays with one machine can hinder a plant's entire operation, which is costly for the company.

Preventive maintenance is a major part of mechanics' jobs. They inspect the equipment, oil and grease moving components, and clean and repair parts. They also keep detailed maintenance records on the equipment they service. They often follow blueprints and engineering specifications to maintain and fix equipment.

When breakdowns occur, mechanics may partially or completely disassemble a machine to make the necessary repairs. They replace worn bearings, adjust clutches, and replace and repair defective parts. They may have to order replacement parts from the machinery's manufacturer. If no parts are available, they may have to make the necessary replacements, using milling machines, lathes, or other tooling equipment. After the machine is reassembled, they may have to make adjustments to its operational settings. They often work with the machine's regular operator to test it. When repairing electronically controlled machinery, mechanics may work closely with electronic repairers or electricians who maintain the machine's electronic parts.

Often these mechanics can identify potential breakdowns and fix problems before any real damage or delays occur. They may notice that a machine is vibrating, rattling, or squeaking, or they may see that the items produced by the machine are flawed. Many types of new machinery are built with programmed internal evaluation systems that check the accuracy and condition of equipment. This assists mechanics in their jobs, but it also makes them responsible for maintaining the check-up systems.

Machinery installations are becoming another facet of a mechanic's job. As plants retool and invest in new equipment, they rely on mechanics to properly situate and install the machinery. In many plants, millwrights traditionally did this job, but as employers increasingly seek workers with multiple skills, industrial machinery mechanics are taking on new responsibilities.

Industrial machinery mechanics use a wide range of tools when doing preventive maintenance or making repairs. For example, they may use simple tools such as a screwdriver and wrench to repair an engine or a hoist to lift a printing press off the ground. Sometimes they solder or weld equipment. They use power and hand tools and precision measuring instruments. In some shops, mechanics troubleshoot the entire plant's operations. Others may become experts in electronics, hydraulics, pneumatics, or other specialties.